Crystal Structure, Electronic Structure, and Optical and Photoluminescence Properties of Eu(III) Ion-Doped Lu₆Mo(W)O₁₂

Abstract

Lu(6)WO(12) and Lu(6)MoO(12) doped with Eu(3+) ions have been prepared by using a citrate complexation route, followed by calcination at different temperatures. The morphology, structure, and optical and photoluminescence properties of the compounds were studied as a function of calcination temperature. Both compositions undergo transitions from a cubic to a hexagonal phase when the calcination temperature increases. All the compositions have strong absorption of near-UV light and show intense red luminescence under a near-UV excitation, which is related to the transfer of energy from the host lattices to dopant Eu(3+) ions. Density functional theory calculations have also been performed. The calculation reveals that hexagonal Lu(6)WO(12) and Lu(6)MoO(12) are indirect bandgap materials, and the near-UV excitations are due to the electronic transitions from the O-2p orbitals to W-5d and Mo-4d orbitals, respectively. The lattice parameters and bandgap energies of hexagonal Lu(6)WO(12) and Lu(6)MoO(12) were determined.

Layer structured Na2Ni(MoO4)2 particles as a visible-light-driven photocatalyst for degradation of methylene blue

“…It has been reported that the optical absorption wavelength positions of charge transfers (CT) in MoO x groups depend on coordination number (CN) x [35]. Dutta et al [36] have reported the summary on CT extension methodologies from molybdates with kinds of crystal space group such as tetragonal, hexagonal, monoclinic, orthorhombic, cubic, and triclinic structures.…”

Luminescent Eu3+-doped NaLa(WO4)(MoO4) and Ba2CaMoO6 prepared by the modified Pechini method

“…However, the technology is limited by the lack of a stable and efficient red phosphor. A much researched group of novel red phosphor materials are the Eu 3+ doped oxides of Mo and W, including compounds such as Ca(W,Mo)O4:Eu 3+ ,Li + [1,2], M + M 3+ (WO4)2−x(MoO4)x:Eu 3+ (M + = Li, Na, K; M 3+ = La, Gd, Y, Lu, Bi) [3][4][5], M6(W,Mo)O12:Eu 3+ (M = Y, Gd, Lu) [6][7][8][9] and AB(W,Mo)O6:Eu 3+ (A = Ca, Sr, Ba; B = Mg, Ca) [10][11][12][13][14][15][16][17][18]. The first two compounds crystallize in the scheelite structure, where there is enhancement of NUV excitation due to non-centrosymmetric lattice sites.…”

Considerable photoluminescence enhancement of LiEu(MoO4)2 red phosphors via Bi and/or Si doping for white LEDs

“…[9] Scheelite-type crystalline structures, such as LiEu(MoO 4 ) 2 , have recently attracted great attention because of their potential applications in the electro-optical field. [ [11][12][13][14][15][16][17][18][19][20] Although the phosphors used in these white LEDs are currently being developed, the red phosphor still suffers from problems of low brightness, low efficiency, and chemical instability. [21] Therefore, if we want to replace the traditional low efficient phosphors designed for lamps, we need to explore novel red phosphors having enhanced chromaticity coordinate, emission efficiency, and thermal stability.…”

“…The intense and broad band can be decomposed into two Gaussian components: A and B. The location of peak A is approximately 274.6 nm, corresponding to the CT (charge transfer ) band of O 2-→Eu 3+ ; the peak of B is approximately 294.9 nm, corresponding to the CT band of O 2-→Mo 6+ [11,18,29]. …”